Chapter 263 Adults choose everything (2 in 1) (page 12)

For the engineers at Institute 14, the current situation is generally a mixed blessing.

The success of Pod No. 1 is a sure sign that at least everyone can be sure that they are going in the right direction.

Therefore, the No. 2 pod now faces at most an engineering design problem, and it may even be a minor problem with the manufacturing or assembly process.

This will have to wait until the test data and the radar data from the anti-aircraft artillery regiment are retrieved before slowly checking.

But for Chang Haonan, achieving this step is obviously not enough.

When he first arrived at the 14th Institute, he used the system to analyze the working principle of the captured pod, so this step was definitely not wrong, and it was the scaled-down version of the No. pod that truly represented his own work.

So no matter what, he still hopes to solve the problem quickly.

About 20 minutes later, aircraft No. 713, which had completed the test, landed steadily on the runway of Yanliang Airport.

Soon, the two pods, one large and one small, were dismantled by ground staff and moved to a workshop specially arranged for No. 14 for testing.

Then Guo Lin and others began to disassemble the pod and check whether there were any problems with the component installation, while Chang Haonan and Xu Yang took down the test equipment on the aircraft.

It can faithfully record the working conditions of various airborne equipment during the entire flight.

In the first two rounds of testing, that is, when the No. 1 pod was activated for interference, everything was normal throughout the process.

But when the No. 2 pod was opened, the situation became very strange.

At the beginning, that is, when the pod had not captured the radar waves directed at it, the data was still normal.

This shows that there is no problem in the power-on step.

However, when the aircraft entered the detection range of the artillery sighting radar and the jamming pod actually entered working status, an abnormality occurred at the signal receiving end.

This was true for both the third and fourth rounds of testing.

And as the distance to the radar body approaches, or as the energy emitted by the jammer increases, the signals recorded by the pod's receiving end become increasingly chaotic.

"Chang Bo."

Just as Chang Haonan frowned and stared at the signal map on the screen, Xu Yang's voice suddenly sounded from behind him:

"Amplify the last minute of the signal from the receiver and take a look."

Chang Haonan's content about signals and control was actually slowly taught by himself after he was reborn.

Of course, thanks to the knowledge provided by the system in several related projects, he is able to handle general application problems with ease.

However, compared with people like Xu Yang who have a professional background, they are still slightly lacking in basic skills training.

Just like now, Chang Haonan may not be able to react faster when he needs to find the real problematic part from a bunch of complicated lines.

But one advantage he has is that he can listen to what others say.

So I immediately followed Xu Yang's request to enlarge and process the last minute records of the last two rounds of testing.

"look here."

Xu Yang pointed at one of the curves:

"The amplitude of this curve is very low at the beginning, almost invisible, but it will increase every cycle from the beginning of its appearance, and in the end it will even be about the same intensity as the gun sight radar wave received by the receiver."

As soon as she said it so abstractly, Chang Haonan immediately grasped the key point:

"So it interferes with the input signal of the entire pod, causing the output signal to be abnormal, and the interference effect on the radar becomes worse..."

"Wait, is this a self-oscillating signal?"

"Yes."

Xu Yang snapped his fingers:

"So the situation is very clear. The problem is not with the components. We can save Guo Gong and others from continuing to investigate."

"call--"

Chang Haonan slapped his forehead with some annoyance, and then called Guo Lin and others who were busy analyzing the circuit board on the other side.

If it's just a simple interference signal, there are actually countless possible sources.

For example, some part of the process in DRFM is not good, or there is a problem with the sampling clock of a certain channel during the frequency division multi-channel sampling process, etc.

But none of these problems can create a positive feedback self-oscillation signal.

The only possibility is that the isolation between the pod's transmitting and receiving antennas is not high enough, and the high-power interference signal emitted by the transmitter is coupled from the receiving antenna into the receiver.

The people at School 14 are also from majors. Although if they were asked to find the problem on their own, they wouldn't be able to spot it like Xu Yang did, but with an explanation, it's definitely not difficult to understand what Chang Haonan meant.

"So that's it..."

Guo Lin also smoothed his hair in surprise:

"But we have obviously implemented polarized isolation?"

The so-called polarization isolation means that the transmitting and receiving antennas are arranged in an orthogonal manner, with one vertically polarized and the other horizontally polarized. Theoretically, there will be no crosstalk between the signals between the two antennas.

However, because it is impossible to achieve truly perfect orthogonal polarization when implemented in engineering, it will still be affected to some extent.

"This shows that our polarization isolation is not high enough. When the distance between the carrier aircraft and the radar antenna reaches a certain level, the power of the transmitter will burn through the polarization isolation, affecting the normal operation of the receiving antenna."

Haonan put down the mouse in his hand, looked at the No. 1 pod not far away and replied:

"And I also understand why Raytheon designed the pod to be such a large size..."

"really……"

Xu Yang, who was the first to raise this question and has been troubled by it, also showed a look of understanding:

"They couldn't solve the problem of polarization isolation, so they used the simplest and crudest physical isolation method. As long as the distance between my transmitting and receiving antennas is far enough, I won't be afraid of being affected."

Now that the problem has been identified, the next step is to find a solution.

In fact, the idea is quite logical.

After all, there are actually only three commonly used sending and receiving isolation methods.

Spatial isolation, polarization isolation and time isolation.

The first type is physically impossible due to the size limit of the pod, and the second type cannot be realized due to technical problems. Naturally, the third type is left.

So Guo Lin expressed his thoughts:

"What if the all-receiver-all-transmit mode is abandoned and the time-sharing working logic of transmitting and receiving is adopted, such as full-pulse store-and-forward interference, or short-pulse store-and-forward interference?"

Xu Yang naturally thought about this, but she still shook her head firmly:

"Then the advantage of our jammer is gone. The short-pulse storage and loop-forwarding jamming only uses a short section of the radar signal to loop forward end-to-end. The false target signal generated will become very wide. A slightly more advanced radar They can easily distinguish real and fake targets."

"As for full-pulse store-and-forward jamming, although the target generated is very real, the false target will lag at least one pulse width behind the real target echo. It is okay to deal with some airborne narrow-width radars, but if it is against something like the Patriot, For linear frequency modulation pulse compression radar, if others directly use a width of 60 microseconds or even 100 microseconds, then our false target will directly lag behind the real target by 10-15 kilometers, and it will not be able to confuse the enemy at all."